Animal feed represents one of the largest costs incurred in keeping livestock and other animals. The use of various enzymes in animal, e.g. livestock, feed has become almost common practice. These enzymes are usually produced by culturing micro-organisms in large scale fermenters operated by industrial enzyme producers. At the end of the fermentation, the resulting “broth” is usually subjected to a series of filtration steps to separate the biomass (the micro-organisms) from the desired enzyme (in solution). Subsequently the enzyme solution is concentrated and processed as a liquid (often after addition of various stabilisers) or to a dry formulation.
For economical and practical reasons, dry enzyme formulations are often preferred to liquid enzymes formulations. Nevertheless, even when a dry enzyme formulation is chosen, some steps of the feed pelleting process, such as conditioning, may be detrimental to the enzyme. Various enzyme manufacturers have developed alternative formulation methods to improve the stability of dry enzyme products during pelleting and storage of the feed. For instance, an option is to coat the enzyme-containing granule with a suitable coating agent.
EP 0 569 468 refers to a formulation consisting of an enzyme-containing granulate that is coated with a high melting wax or fat alleged to improve resistance to pelleting conditions. A disadvantage of such a coating is that the dissolution time of the granulate is long (about one hour). Therefore the bio availability of the enzyme to the animal is decreased. In addition, the granulates have a wide particle size distribution which makes it difficult to obtain an evenly distributed enzyme concentration after coating, since small particles contain a relatively high amount of coating agent as compared to large particles.
WO 00/47060 discloses the use of polyethylene glycol (PEG) as a coating material. These PEG coatings have the disadvantage that they do not increase the pelleting stability of the enzyme granulate to the desired level.
There is thus still a need for stable formulations of enzymes for use in animal feed that are cheap and easy to produce and that combine a satisfactory pelleting stability with good bio availability of the enzyme to the animal.